In the semiconductor industry many sputter etch machines are utilized to remove selected portions of metallization layers. Generally the metallization layer, which may be for example gold, has selected portions masked by some material having a high resistance to sputtering, such as titanium tungsten. To perform the sputter etch procedure one or more semiconductor wafers is positioned on the cathode of the sputter etch machine and essentially acts as the sputtering target. The gold is removed (sputtered) wherever it is not masked by the titanium tungsten.
In the prior art sputter etch machines a quartz plate is positioned in overlying relationship to the cathode to protect the cathode from sputtering also. Generally, the cathode is constructed of some good electrical conductor, such as stainless steel or aluminum alloy, which will sputter relatively easily and contaminate the sputtered gold, thereby, adversely affecting the etching thereof. The quartz plate is constructed coextensive with the cathode and has openings therethrough for receiving the semiconductor wafers therein so that when wafers are properly positioned in the openings, the entire exposed upper surface of the cathode is covered.
The major problem with this procedure is that on occasion the titanium tungsten masking layer is etched through, resulting in the underlying gold being removed in undesired areas. The rejection rate of semiconductor wafers directly attributable to this problem is as high as 10%. This is an especially important problem because the gold sputtering procedure occurs near the end of the fabrication process and each reject means that all of the foregoing time and expense has been wasted. This is, therefore, a serious problem in the semiconductor industry.